Is it necessary to be FOSS, or is free good enough? If cost is the only driver and the backup is local to a regular device, I can recommend SyncBack for simple backups on their free version. I bought Pro several years ago and there is no ongoing licensing fee. When they add certain services I would find useful, or as tech progresses, I’ll upgrade but there’s no ongoing cost and it runs reliably for me. It’s also very windows-centric in terms of its design and UI, which makes it relatively easy to use. Granted I wouldn’t give it to my mother to set up for herself, but it will run unattended once set up.
The question I have is what can we do (in the marketplace of paying devs for indie projects) to prevent them from adding improvements and merely keep the projects compliant as new OSes swap out old libraries? Most of the really good, popular utilities have been ruined by bloat and, in the most successful cases, sale to corporations which instantly enshitify.